The background art in the technical field of the invention is exemplified by European Patent Application No. 0,162,509, U.S. Pat. No. 3,258,895, British Patent Specification No. 859,607 and U.S. Pat. No. 4,311,494.
European Patent document No. 0,162,509 shows a drying process and corresponding apparatus which substantially recover available heat by heat pumping using an expansion/recompression sequence taking place in a subsonic convergent/divergent nozzle. The expansion of the gaseous stream within the convergent portion of the nozzle causes part of the vapor present in the gaseous stream to condense in the form of droplets which are separated inertially from the main stream and collected at or near the throat region of the nozzle. Auxiliary means may be provided at the inlet of the nozzle to initiate and/or enhance the condensation process. Other auxiliary means may be provided to enhance the inertial separation; a cascade of deflecting blades is shown, which induces a swirling action within the accelerating stream. This is turn causes the streamlines of the flowing gaseous medium to follow helico-spiral paths, thus creating a radial pressure gradient within the expanding stream. In fact, this pressure gradient causes differences in the amount of expansion taking place along streamlines at varying radii from the nozzle axis. The portion of the stream travelling along those streamlines nearest the inner wall of the separator undergoes maximum expansion, while those portions travelling on streamlines near the outer wall undergo less expansion and thus less vapor condensation. Furthermore, similar differences between streamlines exist in the centrifugal field which drives the droplets of condensate towards the outer wall of the separator. These differences reduce the capacity of the separator to extract vapor from a given gaseous mixture, but do not greatly impair the exergetic efficiency of the separator.
In this specification the terms "exergetic" and "exergy", are used as follows. Exergy means the fraction of calorific energy of an element or other material which can theoretically be converted to non-calorific energy. To the contrary, anergy is the fraction of the calorific energy which is not convertible into another form of energy. The calorific energy of an element is the sum of its exergy and its anergy. Any thermodynamic transformation occurring without loss of exergy and/or non-thermal energy is called iso-exergetic, and its exergetic efficiency equals unity. Any loss of exergy and/or of non-thermal energy is converted at least partially into anergy, and reduces the exergetic efficiency.
U.S. Pat. No. 3,258,895 shows a device for centrifugal separation of solids from a gaseous medium. In this device, deflecting blades create a swirl within the flowing stream, and straightening blades suppress the swirl after centrifugation and extraction of the particles. Means are provided for preventing re-entrainment of the separated particles. Such means cause flow separation, which is very detrimental to the exergetic efficiency of the process. Flow separation occurs in the inner core of the flowing stream, at locations where no inner wall is present to prevent the spinning fluid from reaching the longitudinal axis of the separator. Altogether, the aforementioned device has a poor exergetic efficiency and thus cannot separate a vapor constituent from a gaseous stream.
British Patent Specification No. 859,607 and its drawings disclose a device for separating suspended solids from fluids including gaseous streams containing vapors. This separator has the shape of a venturi tube having in its throat whirling blades for inducing a swirl in the flowing stream. This induces centrifugal separation within the diverging portion of the venturi tube, where slots and associated particle-catching vanes are provided to extract particles centrifuged to a peripheral wall of the device. In the specification, no mention is made of deliberate flow separation, but flow separation does occur in the diffuser portion of the venturi tube, at locations where no inner wall is present to prevent the spinning fluid from reaching the longitudinal axis of the venturi tube. Thus, significant losses of energy and exergy occur in the main stream, and particle extraction capacity is also lost.
U.S. Pat. No. 4,311,494 shows an axial flow gas cleaning device for separating non-gaseous contaminants from a relatively high velocity gas stream. This centrifugal separator includes means for reducing abrasion of its tubular housing and deflecting elements by the contaminant particles. Notwithstanding these measures and statements in the specification concerning reduction of energy losses in the gaseous stream, whirling blades are provided as shown in FIGS. 2 and 3, thereby causing centrifugal separation to take place in the diffuser portion of the device. As in the above-mentioned British specification, there are substantial losses of energy and exergy in the main stream, along with reduced particle extraction capacity.
To summarize, some of the known processes and equipment exhibit poor exergetic efficiencies, and little or no capacity for separating vapor constituents from gaseous streams. Other processes and devices, while providing higher exergetic efficiency, have a limited capacity for extracting vapor and particulate from gaseous streams. However, there is a need for processes and apparatus with a high capacity for extracting vapor constituents from gaseous streams, coupled with high exergetic efficiency. The principal object of the present invention is to fulfill this need.
Another object of this invention is to provide an improved process and apparatus for at least partial subsonic aerodynamic separation of vaporous condensable components from a multiple component gaseous stream.
Another object of this invention is to provide an improved process and apparatus for at least partial subsonic aerodynamic separation of solid and/or liquid aerosols from a gaseous stream.
Other objects and advantages of the invention will appear from the following description and from the attached drawings.